[Model] Use autoweightloader for mamba

[sfeng33]

Partially fixes #15697
Verified mamba model loaded with following command

vllm serve mistralai/Mamba-Codestral-7B-v0.1

[github-actions]

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[DarkLight1337]

Thanks for helping with this!

[DarkLight1337]

Next time please satisfy the DCO check

[sfeng33]

Thanks for the review!